Reflecting electric lamp



3 c. BIRDSEYE 2,144,400

' REFLECTING ELECTRIC LAMP Filed Dec. 28, 1935 6 iwkzfiazt L9 attorneysPatented 17, 1 939 UNITED STATES PATENT OFFICE nnmcrmc Emo'rmc LAMPClarence Birdseye, Gloucester, Mesa, assignor, by 'mesne assignments, toBirdseye Electric Company, Dover, DeL, a corporation of DelawareApplication December 28, 1935, Serial No. 56,502

8Claims.

For example, in stage-lighting where colored effacts are desired, thisis often accomplished by 15 piacingstandard lamp bulbs behind suitablecolor screens, usually made of gelatine. The color of the light shiningon the stage may be changed by the operator of a key-board, each keycontrolling a single lamp or a series of a given color. In 20 la geinstallations many lamps, each with its screen and external reflector,are employed. Gelatine screens are relatively cheap, but their life isshort and the labor .cost of replacing them perhaps Once a week is high.Permanent color' 25 screens of glass are heavy and expensive, and mustbe replaced frequently because of breakage. Color screens produced bycoating the bulb surface are often inefiicient transmitters. of light,and they temperature of such coatings during the periods of use isv highenough to cause rapid destruction of most colors and binders. Bulbs madeentirely of colored glass are satisfactory within limits for thepurpose, except fortheir first cost, which is generally very high, sincethe 35 colored glass is a relatively expensive material.

I have found that I can reduce the cost and upkeep of such aninstallation for producing colored light eilects, and at the same timeeliminate the need of external reflectors, thus further re- 40 ducingcost and the space required for the installation, and secure thesedesirable results with an appreciable increase in lighting efficiency.This I achieve by employing a composite bulb having part of its surfacemade into a highly efflcient reflector, and preferably of such shape anddisposition relative to'the light source within the bulb that allreflected rays pass directly out of the lamp through the transmittingarea of the bulb, after not more than a single reflection, and

50 by using in combination with such a reflecting portion of the bulb atransmitting portion which is made of colored glass, or in some otherway is different in chemical composition and in light transmittingproperties from the rest of the bulb.

55 Thus the transmitting portion 01 the bulb becomes in effect a windowwithcertain characteristics that are different from the rest of thebulb, and may be of colored glass for the specific case discussed above,but also may be any other glass or material having specific opticalproper- 5 ties different from those of the rest of the bulb, and whichwill in part determine the wave length of the transmitted light.

Such a window of selected glass may be sealed or fused into a bulb in asymmetrical position in its bulbous portion on a line with the main axisor with the axis of the reflecting portion of the bulb. Its size, inthis position, may approximate the maximum diameter of the bulb,although it need not necessarily be hemispherical in shape, since aflatter curve would be equally satisfactory and would require less ofthe selected or colored glass. The rest of the bulb may preferably besilvered over either the inside or outside surface of plain glass, sothat all of the light from the source would either be transmittedthrough the colored window directly as direct light, or after a singlereflection from the silvered surface. If the colored window in a bulb ofthis shape were of smaller size than the maximum diameter of the bulb,and if the're'st of the bulb were silvered, or otherwise made into ahighly efiicient reflecting surface, it is obvious that some of thereflected light would be trapped within the silvered surface, and wouldbe reflected several times before leaving the bulb. This would result ina measurable decrease in lighting-efficiency, 'and'colored windowssmaller'tha'n the maximum diameter of the bulb would be employed onlywhen the sillciency was of secondary importance and when the cut-offangle was the determining consideration. I

Symmetrical lamps of other shapes than the standard shape may be readilyconstructed in this way, but in all such cases the diameter of the 49 Iwindow is preferably that of the maximum bulb diameter in order toobtain highest efflciency; and

in general, substantially the rest of the bulb may be utilized as aneflicient reflector. The reflector, besides directing most of the lightfrom the source through the window, also serves to hood the light sourceand thereby mask the uncolored parts of the bulb.

A window of dissimilar material may alternatively be located in the sidewalls of a bulb, 50 although a less efficient result will be securedbecause of trapped rays and multiple reflection, unless either thewindow covers approximately half the area of a bulb symmetrical aboutits main axis, or unless an asymmetrical bulb is used which has beendesigned to have such shape and provided with a reflecting surface suchthat all of the light leaves the bulb through the window either asdirect light or after a single reflection. Such a bulb with a coloredwindow occupying a part of the side wall. and with a,

sloping neck reflector, and with the rest of the bulb surface serving asa reflector to reflect light directly out through the colored window isan efflcient lamp for stage lighting effects.

In this same manner a quartz window may be sealed into a glass bulb fortransmitting ultraviolet light rays, for example. In general I wish toinclude within the scope of this invention all lamp bulbs having windowsof different transmitting properties than the rest of the bulb, and usedwith reflecting surfaces integral with the bulb to reflect light outthrough the window.

It may be desired in some cases to produce a diffuser! light from suchwindow-bulbs and this may be obtained by frosting the transmittingportion of the bulb, or by frosting the glass under the reflectingdeposit, or in some other way producing a diffusing reflecting surface,as ex-,

plained in the co-pending application Serial No.. 47,581.

These and other features of the invention will be best understood andappreciated from the following description'of two preferred embodimentsthereof selected for purposes of illustration and shown in theaccompanying drawing, in which,

Fig. l is a view in elevation, partly in section, of a lamp ofsymmetrical shape, and

Fig. 2 is a similar viewof a lamp shaped to direct a beam at rightangles to its major axis.

The lamp shown in Fig. 1 has a composite bulb in which is included acylindrical neck portion ill, a flaring or conical portion II and acurved or rounded end portion l2. The neck and body portions l0 and Itmay comprise any glass commonly used in commercial bulbs while the endportion I2 is herein shown as being red glass fused into the body of thebulb.

The lamp includes the usual metallic base It and mount l I through whichproject lead-in wires I! for a coiled coil filament l6. A desirable typeof filament is that disclosed in. the pending application of CharlesSpaeth, Ser. No. 15,605, consisting in a wire helix having a core oftungsten orthe like therein and being wound with its core in a secondaryhelix. As herein shown the filament is arranged in substantiallyV-shaped design disposed transversely to the major axis of the bulb.

The bulb is provided upon a predetermined portion of its surface with aninterior reflecting coating I1 and for this purpose metallic silver maybe satisfactorily employed. In the illustrated lamp the'reflectingcoating ll extends from the line of maximum bulb diameter to aline inthe neck of the bulb and it is supplemented by a reflecting disk l8surrounding and insulated from the lead-in wires just beyond the innerend of the mount M.

In the lamp of Fig. 1 the light rays emanating from the filament it passeither directly out through the red glass end portion l2 or they arereflected by the coating I! or the disk It and pass out as reflectedlight through the portion l2. The coating l1, further, acts to hood thelight of the lamp in all directions except where it is wanted, with theresult that substantially all the light energy of the lamp is conmaximumdiameter, a window of colored glass 'auacoo 1 servedanddirectedintoasingle rcstrictedbeam of red light.

The lamp of Fig. 2 is similar in constmction to that already describedbut of somewhat different shape. Its composite bulb has a cylindricalneck 20 and conical portion 2i disposed with its-axis at right angles tothe axis of the I neck, and both made of clear glass of any commercialtype. The bowl portion 2| may be circular or oval in cross section (in aplane perpendicular to the plane of the paper) and a curved or roundedface 22 of red glass is fused, as before, into the body of the bulb.

The lamp is provided with the usual base 23, and sealed-in mount 24 fromwhich project lead-in and supporting wires 25. In this case the coiledcoil filament 26 is supported in a plane substantially perpendicular. tothe axis of the portion 2| instead of perpendicular to the principalaxis of the lamp.

The inner end of the neck 20 and the entire inner surface of the bowlportion 2i are provided with a coating of metallic silver 21 or othereflicient reflecting material and this is supplemented by a reflectingdisk 28 surrounding the lead-in wires and supporting wires 25 and sodisposed as to constitute in effect a continuation of the surface of thebowl portions 2|. On account of the particular shape of the reflectingsurface, which, as shown may be substantially parabolic, all raysemanating from the filament are collected into a single concentratedbeam and directed outwardly through the red glass portion 22 of thebulb.

While I have illustrated only lamps having red glass window portions itwill be understood that I contemplate the employment of any desiredmaterial in this portion of the lamp. For example, difierent' colors maybe secured by introducing metallic or metalloid ingredients intotheglass composition, or quartz or other light filtering material may beused. These may require other adjustments in the base materials formingthe glass in order to equalize the coemcient of expansion of the fusedportions of the bulb.

. It will be seen that by the present invention I provide a compact andeiflcient unit which may be installed in smallspace or manipulatedconveniently by the user and which is useful in a broad field oflighting, therapeutic treatment and radiant energy application of all.sorts.

The lamp of Fig. 1 is the subject matter of my divisional applicationSerial No. 242,615, filed November 26, 1938, which contains also genericclaims.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent of the United States, is:-

1. An electric lamp comprising a clear glass bulb having a neck, aparabolic portion disposed with its axis at right angles to the axis ofsaid neck and having a metallic reflecting coating thereon, a flattenedoutwardly convex portion of colored glass fused into the dissimilarglass of the bulb as an integral part'thereof and located opposite tosaid parabolic portion, a support projecting out of the neck, and afilament located thereby substantially at the focus of the reflectingsurface.

2. An electric lamp comprising a clear glass bulb having a neck merginginto a substantially conical portion disposed with its axis at rightangles to the neck and having a metallic reflecting surface extendingsubstantially to its line of fused into the dissimilar glass of saidconical portion and presenting an outwardly convex curved transmittingportion of a diameter equal to the maximum diameter of the bulb, and afilament supported in a plane at substantially right angles to the axisof the conical portion of the bulb.

3. An electric incandescent lamp comprising a bulb having a neck merginginto an enlarged substantially parabolic portion disposed with its axisat an angle to the neck and flaring to a line of maximum diameterlocated in a plane beyond the neck, the interior walls of said parabolicportion having a metallic reflecting coating thereon, a substantiallycircular window of material havingdifierent optical properties from theglass of the bulb closing the larger end of said parabolic portion, acoiled tungsten filament supported in the neck of the bulb and centeredin said parabolic portion, and a neck reflector disposed substantiallyin the general contour of the bulb.

